Marine Weather and Tide Forecast for Los Altos Hills, CA

SHORT TERM
Issued at 1157 PM PDT Wed Sep 23 2026 (Tonight through Friday)

There is a large variation in temperatures across our forecast area, with 50s in a shallow marine layer along the coastline and 60s, 70s and near 80 inland and at elevation. The warmth is due to ongoing thermal and height ridging aloft while a narrow channel of cooler air over the coastal waters is undercutting the ridge.
There is very little to no stratus or fog over the coastal waters since there is also warmer surface to near surface air temporarily mixing in on northwest winds. Even though it's dry aloft i.e.
good conditions for outward radiative cooling to help stratus and fog develop, the air/sea interface is not thermodynamically supportive of stratus/fog at the current time. However, 1000 mb NAM forecasts a rapidly southeastward moving cooler air mass arriving in our coastal waters between midnight and Thursday morning, which may briefly fall into syncopation with the remaining rhythm of radiative cooling in the early morning. This combination will likely help produce a few areas of coastal stratus and fog, while inland areas stay clear since the marine layer depth is forecast to remain near steady.

Daytime highs on Thursday will warm up similarly to Wednesday's daytime highs with mid 60s to 70s near the immediate coastline, 70s/80s bayside to the 90s well inland.

The ridge will weaken Friday with onshore winds deepening, sending cooler air inland. Daytime highs Friday will range from the 60s/70s coastside to the 80s well inland.

LONG TERM
Issued at 1157 PM PDT Wed Sep 23 2026 (Friday night through next Wednesday)

For the weekend, 500 mb troughing will return once again which will keep temperatures cooler than normal for late September. It should be a beautiful weekend temperature-wise. After the weekend cooling trend, temperatures will warm up again by the middle of next week.

AVIATION
(12Z TAFS)
Issued at 445 AM PDT Thu Sep 24 2026

Not much in the way of a marine layer this morning. In fact, 12Z TAFs are much more optimistic with mostly VFR. There is some early morning clouds/fog trying to develop, but definitely struggling.
Highest likelihood for LIFR to IFR impacts will be HAF and MRY.
Breezy onshore this afternoon. Low conf for CIGs late tonight as weak front approaches from the NW.

Vicinity of SFO...VFR through the period. 10-20 pct chc of low CIGs toward the end of the TAF with a passing front.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...early morning LIFR CIGs trying to develop around Monterey Peninsula with impacts possible through 16-17Z. VFR this afternoon.

MARINE
(Today through Tuesday)
Issued at 445 AM PDT Thu Sep 24 2026

Light to moderate northerly breezes expected through early Thursday night. Building high pressure after a passing cold front will usher in fresh to strong breezes Friday into Saturday for most of the waters. The stronger winds will lead to an elevated sea state and hazardous conditions for small craft.

FIRE WEATHER
Issued at 450 AM PDT Thu Sep 24 2026

Marine layer is pretty much non-existent overnight. That led much less RH recovery across the district at both lower and higher elevations. NGFS gave us a hit earlier in the night as the Timber Fire had an northern perimeter flare up. Even FireGuard showed the heat as well. Not completely surprised given temps in the 70s and RH recovery around 30 pct near Timber. Otherwise, notes for today will be another mild and dry day across the district. Hottest and driest across the interior portions. Do expect an uptick with winds late tonight and Friday as a dry front moves through. Cooler and wetter for Friday and over the weekend.

MM

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory until 5 AM PDT early this morning for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Friday for Mry Bay.

Small Craft Advisory from 9 AM Friday to 9 AM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm- Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory from 9 PM this evening to 9 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory from 9 AM Friday to 3 PM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.